linux-toradex.git/include/linux/delayacct.h, branch v6.0-rc1

delayacct: track delays from write-protect copy

2022-06-01T22:55:25+00:00

Delay accounting does not track the delay of write-protect copy.  When
tasks trigger many write-protect copys(include COW and unsharing of
anonymous pages[1]), it may spend a amount of time waiting for them.  To
get the delay of tasks in write-protect copy, could help users to evaluate
the impact of using KSM or fork() or GUP.

Also update tools/accounting/getdelays.c:

    / # ./getdelays -dl -p 231
    print delayacct stats ON
    listen forever
    PID     231

    CPU             count     real total  virtual total    delay total  delay average
                     6247     1859000000     2154070021     1674255063          0.268ms
    IO              count    delay total  delay average
                        0              0              0ms
    SWAP            count    delay total  delay average
                        0              0              0ms
    RECLAIM         count    delay total  delay average
                        0              0              0ms
    THRASHING       count    delay total  delay average
                        0              0              0ms
    COMPACT         count    delay total  delay average
                        3          72758              0ms
    WPCOPY          count    delay total  delay average
                     3635      271567604              0ms

[1] commit 31cc5bc4af70("mm: support GUP-triggered unsharing of anonymous pages")

Link: https://lkml.kernel.org/r/20220409014342.2505532-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang 
Reviewed-by: David Hildenbrand 
Reviewed-by: Jiang Xuexin 
Reviewed-by: Ran Xiaokai 
Reviewed-by: wangyong 
Cc: Jonathan Corbet 
Cc: Balbir Singh 
Cc: Mike Kravetz 
Cc: Stephen Rothwell 
Signed-off-by: Andrew Morton

kernel/delayacct: move delayacct sysctls to its own file

2022-04-06T20:43:44+00:00

kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.

To help with this maintenance let's start by moving sysctls to places
where they actually belong.  The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we
just care about the core logic.

All filesystem syctls now get reviewed by fs folks. This commit
follows the commit of fs, move the delayacct sysctl to its own file,
kernel/delayacct.c.

Signed-off-by: tangmeng 
Signed-off-by: Luis Chamberlain

delayacct: track delays from memory compact

2022-01-20T06:52:55+00:00

Delay accounting does not track the delay of memory compact.  When there
is not enough free memory, tasks can spend a amount of their time
waiting for compact.

To get the impact of tasks in direct memory compact, measure the delay
when allocating memory through memory compact.

Also update tools/accounting/getdelays.c:

    / # ./getdelays_next  -di -p 304
    print delayacct stats ON
    printing IO accounting
    PID     304

    CPU             count     real total  virtual total    delay total  delay average
                      277      780000000      849039485       18877296          0.068ms
    IO              count    delay total  delay average
                        0              0              0ms
    SWAP            count    delay total  delay average
                        0              0              0ms
    RECLAIM         count    delay total  delay average
                        5    11088812685           2217ms
    THRASHING       count    delay total  delay average
                        0              0              0ms
    COMPACT         count    delay total  delay average
                        3          72758              0ms
    watch: read=0, write=0, cancelled_write=0

Link: https://lkml.kernel.org/r/1638619795-71451-1-git-send-email-wang.yong12@zte.com.cn
Signed-off-by: wangyong 
Reviewed-by: Jiang Xuexin 
Reviewed-by: Zhang Wenya 
Reviewed-by: Yang Yang 
Reviewed-by: Balbir Singh 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

delayacct: cleanup flags in struct task_delay_info and functions use it

2022-01-20T06:52:55+00:00

Flags in struct task_delay_info is used to distinguish the difference
between swapin and blkio delay acountings.  But after patch "delayacct:
support swapin delay accounting for swapping without blkio", there is no
need to do that since swapin and blkio delay accounting use their own
functions.

Link: https://lkml.kernel.org/r/20211124065958.36703-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang 
Cc: Balbir Singh 
Cc: Ingo Molnar 
Cc: Johannes Weiner 
Cc: Peter Zijlstra 
Cc: Zeal Robot 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

delayacct: fix incomplete disable operation when switch enable to disable

2022-01-20T06:52:55+00:00

When a task is created after delayacct is enabled, kernel will do all
the delay accountings for that task.  The problems is if user disables
delayacct by set /proc/sys/kernel/task_delayacct to zero, only blkio
delay accounting is disabled.

Now disable all the kinds of delay accountings when
/proc/sys/kernel/task_delayacct sets to zero.

Link: https://lkml.kernel.org/r/20211123140342.32962-1-ran.xiaokai@zte.com.cn
Signed-off-by: Yang Yang 
Reported-by: Zeal Robot 
Cc: Balbir Singh 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

delayacct: support swapin delay accounting for swapping without blkio

2022-01-20T06:52:55+00:00

Currently delayacct accounts swapin delay only for swapping that cause
blkio.  If we use zram for swapping, tools/accounting/getdelays can't
get any SWAP delay.

It's useful to get zram swapin delay information, for example to adjust
compress algorithm or /proc/sys/vm/swappiness.

Reference to PSI, it accounts any kind of swapping by doing its work in
swap_readpage(), no matter whether swapping causes blkio.  Let delayacct
do the similar work.

Link: https://lkml.kernel.org/r/20211112083813.8559-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang 
Reported-by: Zeal Robot 
Cc: Balbir Singh 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

delayacct: Add sysctl to enable at runtime

2021-05-12T09:43:25+00:00

Just like sched_schedstats, allow runtime enabling (and disabling) of
delayacct. This is useful if one forgot to add the delayacct boot time
option.

Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/YJkhebGJAywaZowX@hirez.programming.kicks-ass.net

delayacct: Default disabled

2021-05-12T09:43:25+00:00

Assuming this stuff isn't actually used much; disable it by default
and avoid allocating and tracking the task_delay_info structure.

taskstats is changed to still report the regular sched and sched_info
and only skip the missing task_delay_info fields instead of not
reporting anything.

Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Link: https://lkml.kernel.org/r/20210505111525.308018373@infradead.org

delayacct: Add static_branch in scheduler hooks

2021-05-12T09:43:25+00:00

Cheaper when delayacct is disabled.

Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Acked-by: Balbir Singh 
Acked-by: Johannes Weiner 
Link: https://lkml.kernel.org/r/20210505111525.248028369@infradead.org

delayacct: clear right task's flag after blkio completes

2021-05-07T07:26:32+00:00

When I was implementing a latency analyzer tool by using task->delays
and other things, I found an issue in delayacct.  The issue is it should
clear the target's flag instead of current's in delayacct_blkio_end().

When I git blame delayacct, I found there're some similar issues we have
fixed in delayacct_blkio_end().

 - Commit c96f5471ce7d ("delayacct: Account blkio completion on the
   correct task") fixed the issue that it should account blkio
   completion on the target task instead of current.

 - Commit b512719f771a ("delayacct: fix crash in delayacct_blkio_end()
   after delayacct init failure") fixed the issue that it should check
   target task's delays instead of current task'.

It seems that delayacct_blkio_{begin, end} are error prone.

So I introduce a new paratmeter - the target task 'p' - to these
helpers.  After that change, the callsite will specifilly set the right
task, which should make it less error prone.

Link: https://lkml.kernel.org/r/20210414083720.24083-1-laoar.shao@gmail.com
Signed-off-by: Yafang Shao 
Cc: Tejun Heo 
Cc: Josh Snyder 
Cc: Jens Axboe 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds